Ever since the discovery of Ras in 1981, a number of small GTP binding proteins (small G proteins) similar to Ras have been found, and many physiological functions they possess have been studied. These small G proteins have a molecular weight of 20,000-30,000 and do not have a subunit structure. They all specifically bind GDP and GTP, and hydrolyze the thus-bound GTP (GTPase activity) (Hall, A., Science, 249, 635-640, 1990; Bourne, H. R. et al., Nature, 349, 117-127, 1991).
To date, more than 50 kinds of genes encoding these small G proteins have been found from yeast to mammals, forming a superfamily. These small G proteins are largely divided into 5 groups of Ras, Rho, Rab, Arf and others, according to the similarity of amino acid sequences.
Of these, Rho was named so because its gene isolated in the form of cDNA from sea hare neuromuscle encodes a polypeptide having about 35% homology with Ras (Ras homologue) (Madaule, P., Cell, 41, 31-40, 1985).
Rho is specifically ADP ribosylated by C3 enzyme, which is one of the botulinum toxins, and Staphylococcal toxin EDIN, and inactivated (Narumiya, S. and Morii, S., Cell Signal, 5, 9-19, 1993; Sekine, A. et al., J. Biol. Chem., 264, 8602-8605, 1989). Hence, the C3 enzyme and EDIN were used to study the involvement of Rho in cell functions from various aspects.
For example, phosphorylation by myosin light chain (MLC) kinase is considered to enable actin.myosin interaction and initiate contraction of smooth muscle, and the structure of smooth muscle myosin phosphatase which dephosphorylates MLC has been clarified (Shimizu, H. et al., J. Biol. Chem., 269, 30407-30411, 1994). It has been clarified that the activity of myosin phosphatase is, like MLC kinase, under the control of the intracellular signal transduction system and Rho is involved in this mechanism. Moreover, an active Rho bound with GTP has been found to enhance Ca-dependent contraction in a smooth muscle skinned fiber specimen (Hirata, K., J. Biol. Chem., 267,8719-8722, 1992), thereby suggesting that the increase in Ca sensitivity in smooth muscle contraction is caused by the inhibition of myosin phosphatase activity via Rho.
In Swiss 3T3 cell and 3Y1 cell, moreover, Rho-dependent promotion of tyrosine phosphorylation (Kumagai, N. et al., J. Biol. Chem., 270, 8466-8473, 1993) and activation of many kinds of serine/threonine kinases (Kumagai, N. et al., FEBS Lett., 366, 11-16, 1995) have been acknowledged. From this, the presence of plural protein kinases in the downstream of Rho in the signal transduction pathway via Rho has been suggested and, actually, ROCα (Leung, T. et al., J. Biol. Chem., 270, 29051-29054, 1995) [another name Rho-kinase, ROCK-II] and p160ROCK (Ishizaki, T. et al., The EMBO J., 15(8), 1885-1893, 1996) [another name ROCβ, ROCK-I] have been reported as serine/threonine kinase (Rho kinase) activated along with the activation of Rho. It has been also reported that biological distribution of the both enzymes is different (Nakagawa, O. et al., FEBS Lett. 392 189-193, 1996). In addition, it has been reported that this Rho kinase directly phosphorylates myosin phosphatase and inhibits its activity (Kimura, K. et al., Science, 273, 245-248, 1996).
Rho has been documented to be responsible for the activation of not only protein kinase but also lipid kinase (Zang, J. et al., J. Biol. Chem., 268, 22251-22254, 1993), and the presence of phospholipase (PLD) activated by Rho has been also suggested (Siddiqi, A. R. et al., J. Biol. Chem., 268, 24535-24538, 1995).
Control by Rho of the motility of Swiss 3T3 fibroblasts in the presence of serum, motility of keratinocyte 303R by HGF and TPA (12-O-tetradecanoylphorbol 13-acetate), spontaneously occurred and chemoatractant mediated motility of neutrophils have been reported (Takai, Y. et al., Trends Biochem. Sci., 20,227-231, 1995), and control of the permeation of liver cancer cell (MM1 cell), which is one of the metastatic cancer models, through cultured mesothelial layer by the activation of Rho has been reported (Yoshioka, K. et al., FEBS Lett., 372, 25-28, 1995), thereby suggesting the involvement of Rho in cell motility.
Meanwhile, in the cells derived from nerves, such as neuroblastoma, PC-12 cells and the like, retraction of neurite and rounding of the cell by lysophosphatidic acid, which is an activation stimulant of Rho, have been acknowledged. Inasmuch as this retraction can be inhibited by C3 enzyme treatment (Jalink, K. et al., J. Cell Biol., 126, 801-810, 1994) and the formation of ringed structure of podosome, which separates the site where dissolution and absorption of bone take place in the clear zone of osteoclast from the surrounding, is inhibited by C3 enzyme treatment (Zhang, D. et al., J. Cell Sci., 108, 2285-2292, 1995), a deep involvement of Rho in the morphological changes in cells has been suggested.
In addition, C3 enzyme treatment reportedly inhibits activation of an adhesion molecule such as LFA (leukocyte function-associated antigen) and the like, and C3 enzyme treatment reportedly inhibits proliferation of Swiss 3T3 fibroblasts (Yamamoto, M. et al., Oncogene, 8, 1449-1455, 1993). Thus, Rho reportedly controls cell adhesion and cell division via actin cytoskeleton, and is also concerned with the transcription control of c-fos gene (Hill, C. S. et al., Cell, 81, 1159-1170, 1995) and transformation of cell (Khosravi-Far, R. et al., Mol. Cell Biol., 15(11), 6443-6453, 1995).
In view of the inhibition of invasion of dysentery bacillus into epithelial cells by C3 enzyme, a recent report has documented the deep involvement of Rho in bacterial infection (Adam, T. et al., The EMBO J., 15(13), 3315, 1996).
In pregnant rats, moreover, the levels of Rho and Rho kinase are reported to be higher as compared to nonpregnant rats (Niiro, N. et al., Biochem. Biophys. Res. Commun., 230, 356-359, 1997), and deep involvement of Rho and Rho kinase in muscle contraction of uterus for childbirth has been known. Further, integrin (Sueoka, K. et al., Fertility & Sterility, 67(5) 799-811, 1997) considered to be involved in the cell-cell and cell-extracellular matrix adhesion during the stages of fertilization, embryogenesis and embryonidation is known to be activated by Rho (Morii, N. et al., J. Biol. Chem., 267, 20921-20926, 1992).
Hence, it has been made clear that Rho is activated upon receipt of signals from various cell membrane receptors and the activated Rho functions as a molecule switch of a broad range of cell phenomena, such as smooth muscle contraction, cell motility, cell adhesion, morphological changes of cell, cell growth and the like, via actomyosin system.
Smooth muscle contraction is significantly involved in the disease states of hypertension, angina pectoris, cerebrovascular contraction, asthma, peripheral circulation disorder, imminent immature birth and the like; cell motility plays an important role in invasion and metastasis of cancer, arteriosclerosis, retinopathy, immune response and the like; cell adhesion is deeply involved in metastasis of cancer, inflammation, autoimmune disease, AIDS, fertilization and nidation of fertilized egg and the like; morphological change of cell is deeply involved in brain function disorder, osteoporosis, bacterial infection of digestive tract and the like; and cell growth is deeply involved in cancer, arteriosclerosis and the like. Therefore, a drug that blocks the functions of Rho is considered to make a therapeutic agent for these diseases in which Rho plays some role.
At present, however, only C3 enzyme and EDIN can inhibit the actions of Rho. These are proteins which cannot permeate cytoplasm, which prevents their development as a pharmaceutical agent.
On the other hand, inhibition of Rho kinase, which is considered to be present downstream of the signal transduction pathway via Rho, is considered to lead to the inhibition of responses of various cell phenomena due to Rho. However, a specific inhibitor of Rho kinase has not been known to date.
It is expected, therefore, that by searching a compound that inhibits Rho kinase, such Rho kinase inhibitor will be an effective agent for the prophylaxis and/or treatment of the above-mentioned diseases and phenomena relating to Rho, such as hypertension, angina pectoris, cerebrovascular contraction, asthma, peripheral circulation disorder, immature birth, arteriosclerosis, cancer, inflammation, immune disease, autoimmune disease, AIDS, fertilization and nidation of fertilized egg, osteoporosis, retinopathy, brain function disorder, bacterial infection of digestive tract and the like.
The compound of the formula (I) is already known to be useful as an agent for the prophylaxis and treatment of circulatory disorder in coronary, cerebral, renal and peripheral arteries and the like (e.g., a potent and long lasting therapeutic agent of hypertension, angina pectoris, renal and peripheral circulation disorder, and suppressive agent of cerebrovascular contraction and the like), as well as a therapeutic agent of asthma (Japanese Patent Unexamined Publication No. 62-89679, Japanese Patent Unexamined Publication No. 3-218356, Japanese Patent Unexamined Publication No. 4-273821, Japanese Patent Unexamined Publication No. 5-194401, Japanese Patent Unexamined Publication No. 6-41080 and WO95/28387 and the like).
The compound of the formula (II) is already known to be useful as a vasodilator, a therapeutic agent of hypertension, a brain function improving agent, an anti-asthma agent, a heart protection agent, a platelet aggregation inhibitor, a psychosyndrome treating agent, an anti-inflammatory agent and an agent for the prophylaxis and treatment of hyperviscosity syndrome (Japanese Patent Unexamined Publication No. 57-200366, Japanese Patent Unexamined Publication No. 61-227581, Japanese Patent Unexamined Publication No. 2-256617, Japanese Patent Unexamined Publication No. 4-264030, Japanese Patent Unexamined Publication No. 6-56668, Japanese Patent Unexamined Publication No. 6-80569, Japanese Patent Unexamined Publication No. 6-293643, Japanese Patent Unexamined Publication No. 7-41424 and Japanese Patent Unexamined Publication No. 7-277979).
However, these compounds of the formula (I) or (II) are not known to block the functions of Rho or to have Rho kinase inhibitory action.